This invention relates to curing compositions under ultraviolet light. In particular, it relates to a device and method for curing compositions placed on aircraft canopies, which are conventionally made of different layers of a polymeric material, typically combinations of acrylic, polyurethane and polycarbonate.
It is essential in the formation of aircraft canopies, particularly for high speed fighter aircraft such as the F-16, that the material forming the canopy be precisely and uniformly cured so as to prevent irregularity and haze. For fighter pilots, any distortion of the canopy could have serious consequences. It is accordingly necessary to provide a system for layering different compositions for hardness on a canopy which are optically precise, while at the same time being resistant to scratches.
Conventionally, arcylic materials are used for this purpose and they can either be heat-cured or cured under ultraviolet light. Difficulty has presented itself in curing the internal surface of the canopy with a regularity sufficient to meet military specifications. This difficulty arises partly from the high degree of curvature of the canopy and the inability to provide an effective suitable ultraviolet curing process and procedure for such units. Other problems arise from the irregularity of the ultraviolet light source and from ambient conditions about and around the curing zone relative to the ultraviolet light source and also the operative requirements of the light source.
Many different compositions can be used on the canopy for providing different properties and these are illustrated, for instance, in the following patents, patent application and publications: U.S. Pat. No. 4,552,932; U.S. Pat. No. 4,544,466; U.S. Pat. No. 4,319,811; U.S. Pat. No. 4,707,586; U.S. Pat. No. 4,198,465; U.S. Pat. No. 4,263,366; and U.S. Pat. No. 4,308,120; U.S. patent application Ser. No. 158,579, filed Feb. 22, 1988 Applicants DeCamp, Raffo, Bimanand, assigned to Sierracin Corporation, entitled "Electrically Conductive Window and a Method for The Manufacture" and for which the declarations and assignments were signed on Feb. 17, 1988); Lyle H. McCarty, Design News, 102 (1986, September); E. C. Lupton, Plastics Engineering, 59 (1985, January); and C. F. Lewis, Materials Engineering, 40 (1987, November). The contents of the above patents, the patent application and publications are incorporated herein by reference.
It is an objective of the present invention to provide a device and method for curing units, particularly laminated polycarbonate aircraft canopies, and especially those which require great optical clarity. The invention seeks to overcome drawbacks with existing heat or ultraviolet light curing systems.